Effects of hydrogen enrichment on combustion and emissions formation processes in a gasoline rotary engine

摘要

This study aims to numerically investigate the combustion and emissions formation processes in a SI rotary engine fueled with hydrogen-gasoline blends. The RNG k-ε turbulence coupled with a skeletal PRF mechanism were adopted to simulate the engine working process under 0%, 2% and 4% hydrogen volume fractions in CONVERGE software. Results showed that a mainstream flow field along with the rotor movement was formed during the compression stroke. The center of the burned zone would move in same direction with the mainstream flow. Meanwhile, due to the effect of the mainstream flow, the flame propagation in direction of the mainstream flow was expedited. While the flame propagation in contrary direction was retarded, consequently, the unburned mixtures at rear region of combustion chamber suffered incomplete combustion. The distributions of NO and CO emissions were also affected by the flow field. After hydrogen addition, the increased OH, H and O radicals concentrations combined with the intense flow flied accelerated the combustion process, which resulted in the improvement and advancement of in-cylinder pressure and temperature. The increased temperature and the changed chemical reaction path promoted the formation of NO emission. At last, CO emission was decreased with the increase of hydrogen-enrichment fraction.